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Archive for September, 2010

I recently discovered this wonderful book for toddlers and children conceived through IVF with donor eggs. It provides a great basis for parents to begin a natural conversation about “their birth story” with their children. 

The author, Kim Noble, very delicately handles this topic and focuses on how much the child was wanted rather than too many specific details of the process of mommy and daddy needing help to have a baby.  This is a fun and lighthearted read that will be enjoyed by many families.  

One More Giraffe

This book can be purchased on online at Amazon through this link:

http://www.amazon.com/One-More-Giraffe-Kim-Noble/dp/0692005781/ref=sr_1_1?s=books&ie=UTF8&qid=1284345636&sr=1-1

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Well now, that’s a mouthful.  It’s no wonder the medical community comes up with all of these acronyms.  PDG – so much easier to say.   This is also sometimes referred to as PGS – pre-implantation genetic screening.  So, we continue our discussions of genetic testing. My last blog entry was about pre-conception testing, this one is focused on the most common form of testing done after an embryo is growing, but before it is transferred back to the uterus (usually on day 5 or 6). 

So, what is PGD and when would someone decide to use it? 

PGD can only be used when the embryos are fertilized and grown outside of the uterus – like in IVF.  The process of PGD is that the embryologist will take a biopsy of a growing embryo (usually on day 3) and remove one or two cells then usually they send it off to a lab that can test select chromosomes of those cells for a variety of genetic disorders and have the results back before the patients decide which embryos to transfer. This way you are eliminating the embryos that you know have genetic defects(not the standard 23 sets of chromosomes) and are only transferring embryos that are considered “competent” or without defects for the chromosomes tested. 

Who would want to do this testing?

There are a few main reasons that a patient may elect to have PGD testing:

  1. It can improve the likelihood of a successful pregnancy for patients who are at risk for passing along an inherited genetic disease.  This can be for something passed from either the egg or sperm.
  2. It can also be helpful for couples experiencing recurring miscarriages – it can rule out embryo competency as a factor for failure, or alert couples if a higher than expected number of embryos have chromosomal defects to allow for futher testing. 
  3. It can be used to help older women select the best embryos.  In patients with advanced maternal age (starting as early as our late 20s, but really making an impact after our mid-30s), we know the possibilities for chromosomal abnormalities in a woman’s eggs increases as we get older.  And the older you are, the higher the risk for genetic/chromosomal defects.   This is evidenced in the success rates of IVF in young women vs. older women.
  4. Another reason some patients may choose PGD is for family balancing – aka gender selection.   Note: although this is legal in the United States, many other countries do not allow PGD for gender selection. 

PGD cannot guarantee success.  And because it generally tests only about 5 sets of chromosomes that provide the greatest risk for defects, there still are risks for other genetic defects that may be incompatible with life, or result in a baby with health issues.  Often, even if PGD testing is done, the pregnant patient may be counseled to considered CVS or amnio as part of routine pregnancy screening. 

So, while older patients (who are at higher risk that  their eggs that could result in chromosomal abnormalities) may see somewhat higher success rates by using PGD, when using young donor eggs, the success rates may actually drop slightly.  Ask your clinic if they keep statistics on patients similar to you who use PGD vs. those who do not – this may help with your decision making.

Sounds surprising, right?  The reality is that there can be a small number of embryos that do not survive the biopsy and will be lost in the process.   Additionally, there can be cases of misdiagnosis (where it is unclear whether the embryo is competent or may appear to be abnormal).  Some reserachers even suggest that a day 3 embryo may show chromosomal issues that perhaps would be able to self-correct – but there is very little data to date to support this theory.  Additionally, there is some evidence that would suggest a PGD embryo may have a slightly lower likelihood of implantation compared to an embryo that has not been biopsied. 

Often cost can be a significant consideration in deciding whether to do PGD testing.  In the US, PGD testing can cost around $4000 -$5000 or more (depending on which set of chromosomes are tested), in Europe the costs start around $2000 and increase depending on the number of embryos tested and what testing is done.  This can add a significant expense to an IVF cycle – so it is important to understand the risks and benefits for your specific case. 

For all of these reasons, PGD is a procedure that should be discussed with your RE (reproductive doctor) so that together you can come up with the best plan for your particular case and circumstances.

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I’ve participated in some rather interesting discussions recently of what prospective parents (especially those using assisted reproductive services such as IVF or donor egg IVF) might want to consider for genetic screening prior to conceiving.   It turns out, there really aren’t any hard rules or “must use” checklists. 

For the sake of this conversation, we’ll just talk about the tests done prior to any fertility treatments or conception. They are performed on the potential parents (or egg & sperm donors if you are using those) to screen out or minimize the risk for genetic disorders that may be passed down through DNA.  In a future post, I’ll talk about PGD (pre-implantation genetic diagnosis) or CGH (comparative genome hybridization), which are big words for two types of genetic screening that are available after the embryos are formed through IVF, but before they are transferred back to the mother or gestational carrier/surrogate.

Depending on which geneticist, OB, or RE you ask about pre-conception genetic testing, you will likely get a different response.   And if you are doing IVF or other assisted fertility treatment with your own eggs, unless you already know about some inherited genetic disorders in your family that you wish to screen out, you might be less inclined to check every option than if you were selecting an egg donor and had the option of selecting a donor who you know had passed the screening for the potentially “bad stuff”. 

Most clinics that specialize in egg donor treatments (and donor agencies) have been testing their egg donors for STDs along with genetic tests for Cystic Fibrosis and depending on ethnicity or heredity – sometimes Sickle Cell Anemia or Tay Sachs. Some clinics include karyotype testing, to identify and evaluate the size, shape, and number of chromosomes in a sample of body cells. Extra, missing, or abnormal positions of chromosome pieces can cause problems with a person’s growth, development, and body functions.

More recently, a few additional tests are popping up on the common testing list of some clinics.  But even if they are not standard at your clinic, you can usually request them as long as you are willing to bear the expense of the testing.  The two tests that are popping up more these days are:

  • SMA – spinal muscular atrophy
  • Fragile X

Perhaps the best advice aside from discussing this with your RE is to consult with a genetic counselor prior to making your decision.  These tests can become even more important for the person providing the eggs if the genetic heredity of the sperm you are using (your partner or donor sperm) also has genetic weaknesses that may be passed on. 

To date, many patients and doctors have not been so concerned with those last two tests unless the patient or donor has a genetic history, or if the patient happens to know someone with this diagnosis and can see the challenges that may come along with them. In some cases, you may elect not to do these additional tests, but instead do a CVS or amnio to test for them once the fetus is growing. 

I think information and knowledge provide power.  So, the most important thing is to ask questions so you understand exactly what tests are done routinely, and which ones may be recommended or only available if you ask for them. That way you can decide what is best for your family! 

Happy testing!

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